Considerable effort has been directed toward the custom molding or formation of foot impressions or casts which, in turn, may be used to form foot orthotic devices. Early approaches included the use of gauze strips and plaster of paris to build up a casting or custom impression of the foot which, when hardened, was removed from the foot. A positive impression was made inside the hardened casting, and then the negative cast was removed and the orthotic device made from the positive impression.
This procedure was time-consuming, messy, somewhat inaccurate and the custom casting impression which was made was suitable only for making a single positive mold of the foot.
The gauze strip process was improved in a system shown in U.S. Pat. No. 2,593,742 to Friedman. In Friedman a slipper-shaped fabric casting form was substituted for the plurality of gauze strips to make the casting. The pre-shaped slipper form was impregnated with plaster of paris, or some other material which is capable of hardening upon the application of water. Once hardened, the custom casting or impression of the foot was removed from the foot, and again, a positive was made inside the custom casting.
While the approach taken in Friedman reduced some of the messiness and handling problems, there were still substantial disadvantages. The Friedman pre-shaped slipper form only loosely fit the patient's foot, and when moistened with water, the operator had to press or fold the plaster of paris containing cloth down against the foot, which was messy and created folds which detracted from the accuracy of the custom casting. Friedman also had the disadvantage of being capable of making only a single positive foot replica from the custom impression.
Various other custom impression kits are also found in the patent literature. Most of these kits are based upon the use of strips of fabric material or moldable surfaces against which the foot can be held. Typical of these prior art devices are the kits or casting systems disclosed in U.S. Pat. Nos. 1,647,639; 2,136,815; 2,856,633; 2,894,288; 2,907,067; 2,952,082; 2,955,326; 2,961,714 and 3,320,347.
A commercially available moldable surface system for making orthotics is the BIO-FOAM System produced by Smithers Bio-Medical Systems of Kent, Ohio. The BIO-FOAM system is based upon a foam material into which the patient presses his or her foot. The foam deforms to the shape of the plantar surface of the foot, and the deformed foam can be used to make a positive plaster cast of the plantar surface. Casting the arch using the BIO-FOAM system can cause problems in that pushing down on the foam to deform it tends to flatten the arch. Shipping the deformed foam cast from the technician taking the impression to the laboratory making the positive cast also can result in damage to the deformed foam impression.
More recently, water-hardenable resins have been used in connection with knit fabric material to produce a variety of custom impression products. Typical of such resin-based custom casting systems are the kits set forth in our U.S. Pat. No. 5,228,164 for the preparation of a custom last for preparing footwear, and U.S. Pat. No. 6,533,971 for the preparation of an orthopedic impression shirt, both of which patents contain technology useful in the present invention, and accordingly, are incorporated by reference into this application.
In U.S. Pat. No. 5,228,164, an elastic casting sleeve, or tubular shell-forming fabric member, is employed which can be slipped over the patient's foot and has sufficient extensibility and resilience to conform to the foot and present a smooth exterior surface which permits the hardened sleeve to act as a shell for the preparation of custom footwear. The sleeve contains or may have resin added to it which is water activatable so as to harden in a short period of time while on the patient's foot. The hardened sleeve can then be cut off the foot, and it is sufficiently thin and smooth so as to enable its use as a positive casting for the formation of custom footwear over the outside of the hardened sleeve. The interior of the sleeve can also be used to form positive castings in a conventional manner.
It has been found, however, that the use of such casting sleeves for the formation of orthotics that engage primarily the plantar surface of the foot is not very practical. The prior art impression sleeve comes up undesirably high on the patient's foot, and there is a tendency for the elasticity of the fabric to cause the sleeve to “bridge” or “tent” in the area of the arch of the foot. Since orthotics often are designed to provide arch support, such bridging or tenting is highly undesirable.
Accordingly, it is an object of the present invention to provide a custom molded orthopedic casting slipper kit which can be used to create a more accurate impression of a patient's plantar foot surface for subsequent production of a foot orthotic device.
Another object of the present invention is to provide an orthopedic casting slipper which is easy to use and particularly is easily removed after hardening without the need to employ a cast cutter or scissors.
A further object of the present invention is to provide an orthopedic casting slipper kit which can be used to form an impression of a patient's foot, and particularly the plantar surface thereof, in a relatively short period of time with minimal attendant messiness.
A further object of the present invention is to provide an orthopedic casting slipper kit which can be easily used by medical technicians and podiatrists.
The orthotic casting slipper kit and method of the present invention and other objects and features of advantage which will become apparent from, or are set forth in more detail in, the accompanying drawing and following description of the Best Mode of Carrying Out the Invention.